Distillation of metals



Oct. 28, 1952 'r. R. A. DAVEY DISTILLATION OF METALS 2 SHEBT SSHEET 1 Filed July 17, 1950 Patented Oct. 28, 1952 Thomas R.'A. Davey, Port Pirie, S out-h Australia, s

Australia, assignon-to The BrokenQHilljAssdciated wsmelters bou'rne, Victoria, toria Application J uly- 17,- In Australia 15 Claims.

This. inventiop'elates to-"the refining of metals by distillation/andhasbeendevised primarilyto.

recovery I of zinc.

facilitate :.:bh8 separation andfrom 1 leadprcontainingsame, particularly lead 1 t bullion whichvhas. previously beendesilverised by adding zinc thereto.

It has :previously. been proposed to separate.

batch distillation process l zincnirom lead-by a and to recover same in condensing: the zinc vapor; ess a: body/of molten zincii the metallic forms-by zontalz surface which is continually renewed by agitating the metal;

densed in the form: of solid -metal.

Now the general object of this invention is to provideimprovementsin the separation; of

a relatively 'volatile constituent from a. molten. metal: complex and particularly in the recovery a of zinclirom-zinciferous lead; while one: specific object 'iStO; provide ar-continuous treatment =apparatusr;

Accordingly :the t means ,aior separatingand recovering a relatively volatile;constituent :frloma molten metal-com-.

plex i momprising progressively directing o the molten metal by gaseous pr chamber,..:causing in an attenuated conditionwithin: andn'discharging ;same.;-i:-roma lower portion thereof maintaining the interior of the chamberlat alsufficiently low;pressureto cause the saida' volatile constituent to whereby thewapor evolved therein is progressivelycondensed.;,

The expression \iattenuated condition is inany condition in which ace area thereof is large tendedfito comprehend: the free or exposedisurf in proportion: to-- the :volume .of the metal:

Thus the proportionof thevolatile constituent presentin said metalris progressively reduced as themolten metal passesthrough thesaid recovery chamber from theinlet to theoutlet. i

Preferably, the molten metal iscaused to pass the; chamber in the form downwardly through of one or more thin iilms, layers or streams or in the sub-divided condition and said condensing zoneris: preferably arranged more or less ver- Proprietary Australia, a company ew In this prior. proc erous leadwithin U a distillationwchamberi haswan extended-hori- I such vextended surface beressure of not more than'zabou't .10 millimeters-of mercuryaand'rbea ing disposed belowan extended horizontal waterr cooled: surface on which the zinc vapor is con-,

invention broadly :includes,

essnrenfrom an ex- 1 1 ternalbodythereofzinto: an upperzportion' of a.

the .molten metalrto descend the chamberl-H be progressively evaporated therefrom and maintaining. 3;'IB131", tively. cool condensing zone within the chamber 1950, Serial No. 174,206, August -5, 1949 a (Cl. 266-49) tically within the recovery to the exposed surface, oigthe molten metal" pass-a1:

r ing therethrough.

Apparatus in accordance- IOW pressure, means for conupper portion of said maintained under a tinuously supplying to an chamber, the molten metal-to be for continuouslydischarging metal" means for'causmg themoltenmetal to pas downwardly "in I said chamber-and means within the'chamberfor condensing" evolved therein; Inthe preferre stantially vertical elongate ber and is. spaced from a surroundingsubstam tially vertically. extending spreading surface and means I are 1 provided for directing molten metal to the'top ofsuchspreadmg sur face, whereby same is caused to flow downw thereover.

For'this purpose the upper end in surface may be defined by a which] substantially" caused to flow in the form of a relativelyathin stream. v

Alternatively be formed'with ahelical channeh Fora more particular description 0 f exemplary made to the'accompanying drawings; in which? Figurel is a view'in sectional elevationorthe distillation apparatus preferred form of vacuum incorporating the invention;

Figure 2 is a view sectional plan on theline 2-2 ofFigure- 1*,-- 1

Figure 3 is av view to a largerscale 'ofa'por tion of Figure 1, I Figured isa view portion of a vacuum struction, and

Figure 5 is a View shows a modification in the construction-of thespreading. surface.

The. distillation apparatus shown. in Figures" 1, 2 and 301 the drawings.hasbeen.devised primarilv f r the separation of zinc from lead bulchamber of modifled co'n lion/whichhas previously been desilverised by adding zinc thereto.

vessel In which is open at its upper end and chamber in proximity: v

with the invention comprises. a recoverychamber'adaptedto be treated; means.

condition through. w

thereon the metallic vapor:

dr'orm of the invention,na subd ondenser is arranged substantially centrally wit v I the incoming w of saidsp'readhorizontal-weir completely surrounds the r 1 1 condenser and over which the-molten-metal -is the said spreading surface'may embodiments oil the invention,yre,ference'will-be half in plan-and-hali-m in sectional 'elevatiomofa" similar to Figurexland This apparatus comprises a vertical cylindrical 3 which has a vertical vacuum pipe II extendin upwardly through the center of the bottom thereof.

The top of the vessel I projects upwardly through an encircling brick structure I2 and same as supported thereon by a plurality of adjustable levelling screws I3 which are fitted to outwardly projecting lugs I4 on the vessel as shown in Figure 1.

The structure I2 is provided with supply and discharge fiues I2 and I22 respectively whereby furnace gases may be circulated around the vessel to maintain the desired temperature thereof.

The open upper end of the vessel is normally closed by a detachable air-tight and watercooled cover I5, the seal therebetween being formed by a compressed ring I6 of rubber or other suitable material.

An elongated annular water-cooled condenser I! is secured centrally to the under-surface of, and depends vertically from, the cover I with its lower end disposed relatively close to the bottom of the vessel I0. The outer peripheral surface of this condenser is convergent downwardly while its inner peripheral surface is preferably convergent upwardly as shown, and has a diameter substantially greater than that of the vacuum pipe II which projects some distance thereinto. When the apparatus is in use cooling water is circulated through the cover I 5 and condenser I! in any convenient manner.

A downwardly convergent spreading tube I8, which at its upper end is only a little smaller in diameter than the vessel I0, is arranged concentrically within the latter and the upper end thereof which is disposed relatively close to the top of the vessel is machined so as to form a plane surface.

The lower end of the tube I8 is welded to the bottom of the vessel I8 and a flexible joint I9 formed of thin metal is incorporated in the tube near its lower end, whereby same may be supported adjacent its upper end by a plurality of external lugs 20, which rest on brackets 2I secured to the inner periphery of the vessel I0, and which are located thereon by pins 22 which extend through clearance holes in such lugs and brackets.

As these brackets 2| are disposed adjacent to the external lugs I4 for the supporting and levelling screws I3, the machined upper end of the tube I8 may be arranged horizontally by adjustment of the screws.

A circular control ring 23 which is approximately equal in diameter to the upper end of the tube I8 is arranged coaXially above the latter, so as to form a narrow annular slot 24 therebetween and the lower end of this ring is also preferably machined to ensure that this slot is uniform in width.

In the illustrated construction, the control ring is supported on the tube I8 by a plurality of spacing members 25 which may conveniently be formed of wire and which determine the width of the slot 24.

A splash guard in the form of a vertical metal ring 26 is arranged concentrically within and spaced from the upper and lower ends respectively of the tube I8 and control ring 23 and same is supported on a plurality of lugs 21 which project inwardly from the said tube and this splash guard serves to direct downwardly onto the inner peripheral surface of the tube, the molten metal which passes inwardly through the slot 24 as hereafter described.

the molten metal to be acent one end thereof. I0 adjacent the level of t "3, so that such the annular space around site end of such p p 13 29 of molten metal, the f Surface of ich is subjected to atmospheric pressure and which is disposed at a distance slightly less than the height of a barometric column of such metal below the level of the annular slot 24.

Thus when a high uum is produced within the vessel I0, the molten metal is forced by atmospheric pressure into the vacuum chamber until its free surface is disposed somewhat above the slot 24 as shown in Figure 3.

In order to prevent undue disturbance of the molten metal, within theannular well of the chamber by the incoming-metal, the discharge end of the supply pipe 28 preferably icates with a vertical open ended passage 30 which is formed by welding a curved metal plate to the inner surface of the vessel as shown in Figures 1 and 2, the upper end of such passage being disposed above the level of the molten such tube while submerged in a be metal Within the chamber, so that the incoming metal is directed into a lower portion of the annular well.

Accordingly, the head of the molten metal above the level of the annular slot 24 maintains a steady flow through the latter and such metal then passes downwardly in the form of a thin tubular stream over the inner surface of the spreading tube I8 to the bottom of the chamber from which it is progressively discharged through a pipe 3I which has its lower end submerged in a bath 32 of the treated metal, whereby a barometric column of metal is maintained in such pipe to form a vacuum seal.

In using the described apparatus for the treatment of desilverised lead bullion in order to separate the zinc therefrom, bullion at a temperature of about 500-700 C. is supplied to the bath 29 at such a rate that the level therein is maintained substantially constant while the interior of the chamber is evacuated by means of a pump (not shown) which is connected to the vacuum pipe II, so that the pressure therein is reduced to the order of about 10-100 microns of mercury.

It is to be noted that the upper end of the vacuum pipe communicates with the interior of the chamber, only through the lower portion of the central passage in the annular condenser, so that the molten metal descending over. the surface of the spreading tube I8 is subjected to the lowest pressure just prior to its discharge from the chamber.

Thus zinc is progressively evaporated from the molten lead as it descends within the chamber and the depth of the latter is so related to the rate of flow that the zinc content is reduced to the required value before the residual metal is discharged through the pipe 3I.

If desired the fiow of the molten metal over the inner surface of the spreading tube I8 may be retarded such as by covering such surface with wire mesh or by arranging one or more wires or the like helically thereon.

The temperature of the condenser, the outer surface of which is disposed substantially parallel to the surface of the spreading tube I8, is maintained at a temperature lower than the melting point of zinc (viz 420 C.) so that the zinc vapor is progressive'aly conden'sdltliereon in the form of a solid collar whichis designated 33inFigurel.'

It win thus be evident that 'the'condensing V surfaceis disposed as close'as is practicable to the evaporating surface thereby providing the conditions necessary to obtain antoptimum separation of zinc;

It will be apparent that during its downward passage over the-spreadingtube [8, the, molten lead suffers a fall in temperature e'quivalenttov the latent heat off the zinc evaporated therefrom but such loss'of heat' is partly compensated by conduction through the spreading tube from the" molten metal surrounding the'latte'r. 1 In any event when the'molten'metal is supplied at"a sufliciently high temperature, the". heat so" lost is not sufficient to impair theefficiency of thefoperation." f If, however, the molten metal'is supplied to' the chamber at a lower temperature,- such'ithat the heat'lost within the chamber 'wouldbtherwise impair the efiiciency of separation, the construction of the vacuum chamber may be modified;as

shown in Figure 4 'in'order that the lower'portion of the spreading "tube" maybe heated by means of burners to compensate for'the loss of heat due to" evaporation and'the'heat sosup plied maybe sumcient to raise the temperature of the outgoing metal above that'of the metal entering thechamber. i

When the collar-33 of condensed zinc has ac denser, means for progressively upper portion of the chamberfthemolten "metal to be treated, means for directing'the'nietal so supplied to the chamber to an upperfpartion r said spreading s rface whereby it flows: own wardly 'thereover in the form of a ,thinf'tiibular stream and means for dischargi ng from' a lower t portion or the chamber the treated moltfi'mtal.

cumulated'to a sufiicient extent; the operation is.

suspended by restoring atmospheric pressureremoval therefrom of the collar 33 of zinc' metal. If the collar should tend to slip downwardly on the condenser while the apparatus is in use, the exterior surface of the condenser may advantageously be provided with spaced longitudinally extending ribs as shown in broken lines at 35 in Figure 2.

' In the modified construction shown in Figure 5 a substantially helical channel 36 is provided on theinn'er surface of the spreading tube by welding thereto the lower edge of an inclined strip of metal, the channel being thus of triangula and downwardly convergent shape in cross-section, so that the free surface area of the molten metal which flows downwardly therethrough is large in relation to the volume thereof.

In this construction the molten metal passes vergent inwardly facing -spreading surface which? extends around and is spaced from the con- 'thecondenser.

"2. Apparatus for separating and rec'overingfa' relatively volatile constituent from a "molten metal complex comprising'a vacuum chamber; a vertically elongated condenser arranged can? trallywithin the 'chambena substantially'icylin drical but downwardly convergent spreading tube" arranged concentrically about the'condenser with its "upper surface disposed in a "horizontal plane,

said" vacuum chamber'being soshaped asjto form around the upper end'portion at"leastfdfthe spreadingtube, an annular reservoir 'for"""the' molten metal "to'be treated, means for directing the molten metal into the'reservoirwherebyiit overflows the'upper endof said spreadingtube and 'thendownwardly over the inner surface of the latter as a thintubular stream, means for discharging the treated molten'metaljfrom a lower portion'of the vacuum 'chamberjand ad justable levelling means supporting the vacuum l ,7 e 3. Apparatus according to claim'2 including'a ring arranged above and spaced fromthe upper end'of said spreading tube'to form therebetween' a narrow substantially continuous a'nniflarslot through which the -molten 'metal'passes to the inner surface of the spreading tube.

4;"Apparatus forseparating'and recoveringa relatively volatile constituent from a-niolten metal complex comprising a vacuum chamber open at the top, a removable cover normally closing and sealing the upper endof the chamber; a

vertically disposedf condenser securedto the underside of said cover and depending therefrom centrally within the chamber, 'said condenser having a centralpassage formed therein' and ex-- tending upwards from the lower end-thereof,

means fixed to the vacuum chamberandforining concentrically around the condenser a substantially cylindrical inwardly facing spreadings face, means for progressively supplying to an) upper portion of said spreading surfaceQ-the molten metal to be treated, means'for discharging the treated molten metal from a lower portion of the chamber and a Vacuum pipefixed to said'chamber and'extending upwards into'and spaced'from, the-wall of said central passage of '5. Apparatus for separating and recovering a relatively volatile constituent from a molten metal complex comprising a vacuum "chamber; which is open at itsupper end, a removable'cover normally closing andsea'ling' said 'uppere'nd of the chamber, a vertically disposed condensate: cured to the underside of the cover anaaepe a-f ing therefrom,=the lower end portion at least pf said condenser being formed with a central pas}- sage, means fixed to the vacuum; chamber and forming a substantially cylindrical and inwardly facing spreading surface which is spaced from and arranged substantially concentrically;about the condenser; means for progressively supplying the molten metal to be treated'toan upper por-' tion of the spreading'sur'face, means for; progre'ssively discharging molten metal 'fi'orn---the i lower end portion of the chamber and a l vac iium supplying w an" the vacuum chamber and extending into said central passage in the condenser.

6. Apparatus for separating zinc from zinciferous lead by vacuum distillation comprising a vacuum chamber which is open at its upper end, a cover normally closing and forming an air-tight seal with the upper end of the chamber, a vertical annular condenser secured to and depending from the underside of the cover within the chamber with its lower end disposed somewhatabove the bottom thereof a substantially cylindrical downwardly convergent spreading tube arranged concentrically about the condenser and having its upper end arranged to form an annular weir, a control ring arranged coaxially above the weir and defining therebetween a narrow slot, an annular reservoir surrounding the said weir with its inner wall formed by said control ring and said spreading tube, a passage for supplying molten metal to said annular reservoir by atmospheric pressure whereby the level of the molten metal in said reservoir is normally disposed above the weir so that same flows through the said narrow slot and then downwardly over the inner surface of the spreading tube in the form of a thin tubular stream, a discharge outlet at the lower end of the vacuum chamber for the treated molten metal, said outlet communicating with a discharge passage of such length and disposition as to accommodate a barometric column of the molten metal and a vacuum pipe extending upwardly through the bottom of the chamber and into the central passage in the condenser.

7. Apparatus according to claim 6 wherein said spreading tube is arranged wholly within and is spaced from the wall of the vacuum chamber and incorporates a flexible joint adjacent the lower end thereof and including adjustable supporting and levelling means for the chamber and means extending through said annular reservoir and supporting said spreading tube adjacent its upper end on the wall of said chamber.

8. Apparatus for separating and recovering a relatively volatile constituent from a molten metal complex comprising a vacuum chamber, a vertically elongated condenser arranged approximately centrally within the chamber, means defining within the chamber a substantially vertically extending and substantially cylindrical inwardly facing evaporating zone which extends around and is spaced from said condenser, the upper end portion at least of said last mentioned means being spaced inwardly from the wall of the chamber to form therebetween and within the chamber a well to contain a body of the molten metal to be treated, means forming a passage for the supply of molten metal from the exterior of the chamber to said well, means for the continuous discharge of molten metal from said well to the upper end of said evaporating zone, and means forming a passage for the discharge from the lower end portion of said chamber of molten metal low in said volatile constituent.

9. Apparatus for separating and recovering a relatively volatile constituent from a molten metal complex comprising a vacuum chamber, a vertically elongated condenser arranged approximately centrally within the chamber, means defining within the chamber a substantially vertically extending and substantially cylindrical inwardly facing evaporating zone which surrounds and is spaced from said condenser, the upper end portion at least of said last mentioned means being spaced inwardly from the wall of said chamber to form therebetween and within the chamber a substantially annular well to contain a body of the molten metal to be treated, a control ring arranged coaxially above and close to the upper end of said means defining the evaporating zone whereby a narrow substantially continuous slot is formed therebetween and about the condenser for the inflow of molten metal from said well to the upper end of the evaporating zone, means forming a passage for the supply to saidwell of molten metal from the exterior of the chamber and means forming a passage for the discharge of molten metal low in said volatile constituent from the lower end portion of the chamber inwardly of said evaporating zone.

10. Apparatus for separating and recovering a relatively 'volatile constituent from a molten metal complex comprising a vacuum chamber, a vertically elongated condenser arranged approximately centrally within the chamber, a substantially vertically disposed and substantially cylindrical spreading member surrounding and spaced from the condenser, said cylindrical spreading member being spaced inwardly from the wall of the chamber and having its lower end connected to the bottom thereof whereby an annular well for molten metal is formed therebetween, means forming a passage for the supply of molten metal to said well from the exterior of the chamber, means for continuously discharging molten metal from the upper end portion of said well and distributing same around the inner periphery of the upper end portion of said spreading member whereby same flows downwards thereover and means forming a passage for the discharge of molten metal low in said volatile constituent from the lower end portion of the chamber inwardly of said spreading member therein.

11. Apparatus for separating and recovering a relatively volatile constituent from a molten metal complex comprising a vacuum chamber, a vertically elongated condenser arranged approximately centrally within the chamber, a substantially vertically disposed and substantially cylindrical spreading tube surrounding and spaced from the condenser and connected at its lower end to the bottom of the chamber, said spreading tube being spaced inwardly from the wall of the chamber to form therein a substantially annular well for the molten metal to be treated, a control ring arranged coaxially above the upper end of the spreading tube and spaced from the latter to form therebetween'a narrow substantially continuous circumferential slot through which molten metal may pass from the well to the interior of said spreading tube, means forming a passage for supplying molten metal to said Well from the exterior of the chamberand means forming apassage for discharging molten metal from the lower end portion of the chamber inwardly of said spreading tube.

12. Apparatus for separating and recovering a relatively volatile constituent from a molten metal complex comprising a vacuum chamber, a vertically elongated condenser arranged substantially centrally within the chamber, a substantially vertically disposed and substantially cylindrical spreading tube surrounding and spaced irom the condenser Within the chamber with its upper end disposed substantially in the horizontal plane, means supporting said spreading tube adjacent its upper end, means including a flexible joint connecting the lower end of said spreading tube to the bottom of the chamber, said spreading tube being spaced inwardly from the wall of the chamber whereby an annular well is formed therebetween and within the chamber, a control ring arranged coaxially above the upper end of the spreading tube and spaced therefrom to form a narrow circumferential slot therebetween and through which molten metal may pass from said well to the interior surface of said spreading tube, means forming a passage for the supply of molten met-' a relatively volatile constituent from a molten metal complex comprising a vacuum chamber which is open at its upper end, a detachable cover normally closing and sealing said open upper end of the chamber, a substantially vertically disposed condenser secured to and depending from said cover approximately centrally within the chamber and having its lower end disposed above but adjacent to the bottom of the latter, said supporting said 1 Apparatus for separating and recovering condenser being formed with a central passage which extends upwardly therein from its lower end, a vacuum pipe fixed to said chamber and extending upwardly into and spaced from the Wall of said passage in the condenser, a vertically elongated tubular spreading means surrounding and spaced from the condenser, means for supplying molten metal to be treated to the upper portion of the interior of said spreading means whereby it flows downwardly therein and in lateral opposition to said condenser and means forming a passage for the discharge of molten metal low in said volatile constituent from the lower end portion of the chamber inwardly of said spreading means.

15. Apparatus for separating and recovering a relatively volatile constituent from a molten metal complex comprising a vacuum chamber, a substantially vertical condenser disposed approximately centrally withinthe chamber and pendent from the top thereof, said condenser having its lower end disposed above but adjacent to the.

bottom of the chamber and having therein a substantially central passage which extends upwardly from its lower end, means forming a vacuum passage which communicates directly with said central passage in the condenser whereby the interior of said chamber is maintained under vacuum by the withdrawal of gases therefrom through said passage in the condenser, means forming a vertically extending evaporating zone around and spaced from the condenser,

means for supplying molten metal to be treated to the upper end portion of said evaporating zone 1 andmeans for discharging molten metal low in i said volatile constituent from the lower end portion of said chamber.

THOMAS R A. DAVEY.

REFERENCES CITED The following references are of record in the file of this patent: I

4 UNITED STATES PATENTS Number I Name Date 2,239,370 Osborn et a1. Apr. 22, 1941 2,239,371 Osborn et a1. Apr. 22, 1941 

15. APPARATUS FOR SEPARATING AND RECOVERING A RELATIVELY VOLATILE CONSTITUENT FROM A MOLTEN METAL COMPLEX COMPRISING A VACUUM CHAMBER, A SUNSTANTIALLY VERTICAL CONDENSER DISPOSED APPROXIMATELY CENTRALLY WITHIN THE CHAMBER AND PENDENT FROM THE TOP THEREOF, SAID CONDENSER HAVING ITS LOWER END DISPOSED ABOVE BUT ADJACENT TO THE BOTTOM OF THE CHAMBER AND HAVING THEREIN A SUBSTANTIALLY CENTRAL PASSAGE WHICH EXTENDS UPWARDLY FROM ITS LOWER END, MEANS FORMING A VACUUM PASSAGE WHICH COMMUNICATES DIRECTLY WITH SAID CENTRAL PASSAGE IN THE CONDENSER WHEREBY THE INTERIOR OF SAID CHAMBER IS MAINTAINED UNDER VACUUM BY THE WITHDRAWAL OF GASES THEREFROM THROUGH SAID PASSAGE IN THE CONDENSER, MEANS FORMING A VERTICALLY EXTENDING EVAPORATING ZONE AROUND AND SPACED FROM THE CONDENSER, MEANS FOR SUPPLYING MOLTEN METAL TO BE TREATED TO THE UPPER END PORTION OF SAID EVAPORATING ZONE AND MEANS FOR DISCHARGING MOLTEN METAL LOW IN SAID VOLATILE CONSTITUENT FROM THE LOWER END PORTION OF SAID CHAMBER. 